Processors

Question 1

What are the registers used inside a CPU?

Explain what the Control Unit and ALU is and how it fits in with these registers

Eight total registers

Answer 1

Program counter (PC)
Memory Address Register (MAR)
Memory Buffer Data (MBR)
Istruction Register (IR)
Accumulator (ACC) or General Purpose Register (GPR)
Stack Poiner (SP)
Condition Code Register (CCR)

The control unit coordinates the CPU by outputting control signals to these registers and the ALU, keeping track of the sequence/steps of the CPU’s operation.

ALU is what conducts the numerical operations; Arithmetic (Add, subtract), Logical (AND, OR, XOR, shifts, etc) and Compound (multiply and divide)

Question 2

Explain opcodes and operands

Answer 2

An opcode is a machine instruction interpretted by the processor to perform a function

set of opcodes is called an instruction set

An instruction set is tied to a process.

Question 3

Explain what a micro-program is and how it ties in with the opcodes and the fetch-decode-execute cycle. What is the fetch-decode-execute cycle

Answer 3

A micro-program is a program stored in memory that is executed by the CPU to perform a a set of specific operations. It is composed of micro-instructions (e.g. MAR <- PC)

The fetch-decode-execute cycle is a conceptual model of how the CPU operates (it can be shown as a set of micro-instructions). When the opcode is decoded, then the associated micro-program/s are executed and then its repeated.